code: def test_tranformed_ts_index(self):
      # DateTimeIndex
      transformed_series = self.target.window_transform(
          {"function": "sum"}
      )
      assert (
          self.target._time_index.__class__
          == transformed_series._time_index.__class__
      )
      # length index should not change for default transformation configurations
      assert len(self.target._time_index) == len(
          transformed_series._time_index
      )
      # RangeIndex
      transformed_series = self.series_from_values.window_transform(
          {"function": "sum"}
      )
      assert (
          self.series_from_values._time_index.__class__
          == transformed_series._time_index.__class__
      )
      assert len(self.series_from_values._time_index) == len(
          transformed_series._time_index
      )
  
file_path: darts/darts/tests/dataprocessing/transformers/test_window_transformations.py
imports: import itertools
  import numpy
  import pandas
  import pytest
  from darts import TimeSeries
  from darts.dataprocessing.pipeline import Pipeline
  from darts.dataprocessing.transformers import Mapper, WindowTransformer
label_desc: Use image node_id 5 for calling the TestTimeSeriesWindowTransform obj's underlying member method code with example usage: obj.test_tranformed_ts_index() without return types